Recently, in order to inspect the processed and manufactured state of a fine structure having a complicated stepped structure due to miniaturization and refinement of electronic and mechanical parts, a high measurement accuracy to size, shape, and surface roughness has been required.
Therefore, a size measuring method using an optical two-dimensional measuring apparatus and a shape or a thickness (surface roughness) measuring method using an optical three-dimensional measuring apparatus are used now in measurement of small-sized electronic and mechanical parts.
As one of conventional optical three-dimensional measuring apparatuses, white-light scanning interferometry (WSI) has been proposed.
With reference to FIG. 7, the WSI uses a principle, in which when a reference beam and an object beam obtained by splitting light generated from a light source 100 by a beam splitter 200 are respectively reflected by a reference surface of a reference minor 400 and a measurement surface (P) of a target object 300 to be measured, and generate an interference signal, a light detecting element 500 captures the interference signal and then analyzes the signal. That is, the WSI measures a three-dimensional shape by detecting a position using a characteristic, in which the interference signal is generated only when the reference beam and the object beam pass through the same optical path.
When interference signals at respective measurement points within a measurement region are observed using the above principle while moving the object at minute intervals in the optical axial direction with a transfer unit, such as a PZT actuator, a short interference signal is generated at a position of each of the points, where the measurement beam has the same optical path as that of the reference beam.
Therefore, when the interference signal generating positions of all the measurement points within the measurement region are calculated, data regarding the three-dimensional shape of the measurement surface are obtained, and thickness and shape of a thin film layer are measured from the obtained three-dimensional shape data.
A measuring apparatus using white-light scanning interferometry is used in the measurement of the film thickness of a dielectric multi-layered film or the analysis of the structure of a continuum (diffuser), for example, the eye ground or the skin, as well as in the measurement of the three-dimensional shape of a fine structure.
However, with the conventional measuring apparatuses, the two-dimensional measuring apparatus to measure the size of a target object to be measured and the three-dimensional measuring apparatus to measure the shape and thickness (surface roughness) of the object are independently designed and separately used, and thus are alternately used to measure the two-dimensional size and the three-dimensional shape of the object, thereby causing troublesomeness.
Further, in case that the conventional three-dimensional measuring apparatus is used, the three-dimensional measuring apparatus obtains an interference pattern by scanning the overall dimensions of a target object to be measured and detects whether or not the object is defective using the interference pattern, and thus has a low inspection speed.